﻿<!DOCTYPE html>
<html>
<head>
  <title>Draggable Link Labels That Stay On Path</title>
  <!-- Copyright 1998-2021 by Northwoods Software Corporation. -->
  <meta name="description" content="This variation on the LinkLabelDraggingTool extension restricts link labels to stay on the link's route while the user is dragging it." />
  <meta name="viewport" content="width=device-width, initial-scale=1">

  <script src="../release/go.js"></script>
  <script src="LinkLabelOnPathDraggingTool.js"></script>
  <script src="../assets/js/goSamples.js"></script>  <!-- this is only for the GoJS Samples framework -->
  <script id="code">
    function init() {
      if (window.goSamples) goSamples();  // init for these samples -- you don't need to call this
      var $ = go.GraphObject.make;

      myDiagram =
        $(go.Diagram, "myDiagramDiv", // the ID of the DIV HTML element
          {
            layout: $(go.ForceDirectedLayout,
              { defaultSpringLength: 50, defaultElectricalCharge: 50 }),
            "undoManager.isEnabled": true
          });

      // install the LinkLabelDraggingTool as a "mouse move" tool
      myDiagram.toolManager.mouseMoveTools.insertAt(0, new LinkLabelOnPathDraggingTool());

      myDiagram.nodeTemplate =
        $(go.Node, go.Panel.Auto,
          { locationSpot: go.Spot.Center },
          $(go.Shape,
            {
              fill: "orange",  // default fill color
              portId: "",
              fromLinkable: true,
              fromSpot: go.Spot.AllSides,
              toLinkable: true,
              toSpot: go.Spot.AllSides,
              cursor: "pointer"
            },
            new go.Binding("fill", "color")),
          $(go.TextBlock,
            { margin: 10, font: "bold 12pt sans-serif" },
            new go.Binding("text"))
        );

      myDiagram.linkTemplate =
        $(go.Link,
          {
            routing: go.Link.AvoidsNodes,
            corner: 5,
            relinkableFrom: true,
            relinkableTo: true,
            reshapable: true,
            resegmentable: true
          },
          $(go.Shape),
          $(go.Shape, { toArrow: "OpenTriangle" }),
          $(go.Panel, "Auto",
            // mark this Panel as being a draggable label, and set default segment props
            { _isLinkLabel: true, segmentIndex: NaN, segmentFraction: .5 },
            $(go.Shape, { fill: "white" }),
            $(go.TextBlock, "?", { margin: 3 },
              new go.Binding("text", "color")),
            // remember any modified segment properties in the link data object
            new go.Binding("segmentFraction").makeTwoWay()
          )
        );

      // create a few nodes and links
      myDiagram.model = new go.GraphLinksModel([
        { key: 1, text: "one", color: "lightyellow" },
        { key: 2, text: "two", color: "brown" },
        { key: 3, text: "three", color: "green" },
        { key: 4, text: "four", color: "slateblue" },
        { key: 5, text: "five", color: "aquamarine" },
        { key: 6, text: "six", color: "lightgreen" },
        { key: 7, text: "seven" }
      ], [
          { from: 5, to: 6, color: "orange" },
          { from: 1, to: 2, color: "red" },
          { from: 1, to: 3, color: "blue" },
          { from: 1, to: 4, color: "goldenrod" },
          { from: 2, to: 5, color: "fuchsia" },
          { from: 3, to: 5, color: "green" },
          { from: 4, to: 5, color: "black" },
          { from: 6, to: 7 }
        ]);
    }
  </script>
</head>
<body onload="init()">
<div id="sample">
  <div id="myDiagramDiv" style="background-color: whitesmoke; border: solid 1px black; width: 100%; height: 600px"></div>
  <p>
    This sample demonstrates a custom Tool, LinkLabelOnPathDraggingTool, that allows the user to drag the label of a Link,
    but that keeps the label exactly on the path of the link.
    The tool is defined at <a href="LinkLabelOnPathDraggingTool.js">LinkLabelOnPathDraggingTool.js</a>.
  </p>
  <p>
    The label on the link can be any arbitrarily complex object.
    It is positioned by the <a>GraphObject.segmentIndex</a> and <a>GraphObject.segmentFraction</a> properties.
    The segmentIndex is set to NaN such that the whole link path acts as the segment, and the segmentFraction is set by the LinkLabelOnPathDraggingTool.
    A two-way data binding on segmentFraction automatically remembers any modified value on the link data object in the model.
  </p>
  <p>
    The tool is derived from a similar tool, <a href="LinkLabelDraggingTool.js">LinkLabelDraggingTool.js</a>,
    that allows the user to drag the label in any direction from the mid-point of the Link path.
  </p>
</div>
</body>
</html>
